This invention relates to a bendable drilling sub and in particular to an adjustable, bendable drilling sub.
So-called bent subs already exist. An example of such a sub is described in U.S. Pat. No. 4,745,982, which issued to K.H. Wenzel on May 24, 1988. The Wenzel sub includes a bent mandrel and sleeve or housing, which is also bent. The desired angular adjustment or bend between a downhole motor above the uphole end of the bent sub and the downhole or bit end of the bent sub is achieved by rotating the housing relative to the mandrel. The Wenzel device relies on accurately machined or cast mandrels and housings. Similarly, the adjustable sleeve is locked to the mandrel for rotation therewith clutches defined by two sets of mating teeth on the housing and on the sleeve. It will be readily apparent that such a complicated structure must be expensive to produce.
The object of the present invention is to overcome the problems inherent to devices of the type described above by providing a relatively simple bendable drilling sub.